# 第一步

最簡單的 FastAPI 檔案可能看起來像這樣：

{* ../../docs_src/first_steps/tutorial001.py *}

將其複製到一個名為 `main.py` 的文件中。

執行即時重新載入伺服器（live server）：

<div class="termy">

```console
$ <font color="#4E9A06">fastapi</font> dev <u style="text-decoration-style:single">main.py</u>
<font color="#3465A4">INFO    </font> Using path <font color="#3465A4">main.py</font>

# First Steps { #first-steps }

The simplest FastAPI file could look like this:

{* ../../docs_src/first_steps/tutorial001_py39.py *}

Copy that to a file `main.py`.

Run the live server:

<div class="termy">

```console
$ <font color="#4E9A06">fastapi</font> dev <u style="text-decoration-style:solid">main.py</u>

  <span style="background-color:#009485"><font color="#D3D7CF"> FastAPI </font></span>  Starting development server 🚀

# Erste Schritte { #first-steps }

Die einfachste FastAPI-Datei könnte wie folgt aussehen:

{* ../../docs_src/first_steps/tutorial001_py39.py *}

Kopieren Sie das in eine Datei `main.py`.

Starten Sie den Live-Server:

<div class="termy">

```console
$ <font color="#4E9A06">fastapi</font> dev <u style="text-decoration-style:solid">main.py</u>

	return signature
}

func newPostRequestV2(endPoint, bucketName, objectName string, secretKey string, formInputData map[string]string) (*http.Request, error) {
	// Expire the request five minutes from now.
	expirationTime := UTCNow().Add(time.Minute * 5)
	// Create a new post policy.
	policy := newPostPolicyBytesV2(bucketName, objectName, expirationTime)
	// Only need the encoding.

	fmt.Println(bytes.ContainsFunc([]byte("World"), f))
	// Output:
	// false
	// true
}

func ExampleCount() {
	fmt.Println(bytes.Count([]byte("cheese"), []byte("e")))
	fmt.Println(bytes.Count([]byte("five"), []byte(""))) // before & after each rune
	// Output:
	// 3
	// 5
}

func ExampleCut() {
	show := func(s, sep string) {
		before, after, found := bytes.Cut([]byte(s), []byte(sep))

(It's not a subtraction, just idiosyncratic syntax.)
The frame size <code>$24-8</code> states that the function has a 24-byte frame
and is called with 8 bytes of argument, which live on the caller's frame.
If <code>NOSPLIT</code> is not specified for the <code>TEXT</code>,
the argument size must be provided.
For assembly functions with Go prototypes, <code>go</code> <code>vet</code> will check that the

01BC          ; mapped                 ; 01BD          # 1.1  LATIN CAPITAL LETTER TONE FIVE
01BD..01C3    ; valid                                  # 1.1  LATIN SMALL LETTER TONE FIVE..LATIN LETTER RETROFLEX CLICK
01C4..01C6    ; mapped                 ; 0064 017E     # 1.1  LATIN CAPITAL LETTER DZ WITH CARON..LATIN SMALL LETTER DZ WITH CARON

///

### Importar las dependencias { #import-the-dependencies }

Este código vive en el módulo `app.routers.items`, el archivo `app/routers/items.py`.

Y necesitamos obtener la función de dependencia del módulo `app.dependencies`, el archivo `app/dependencies.py`.

     * cancelled.
     */
    @Nullable Executor delegate;

    /**
     * Set before calling delegate.execute(); set to null once run, so that it can be GCed; this
     * object may live on after, if submitAsync returns an incomplete future.
     */
    @Nullable Runnable task;

    /** Thread that called execute(). Set in execute, cleared when delegate.execute() returns. */

Now, let's see the module at `app/main.py`.

Here's where you import and use the class `FastAPI`.

This will be the main file in your application that ties everything together.

And as most of your logic will now live in its own specific module, the main file will be quite simple.

### Import `FastAPI` { #import-fastapi }

You import and create a `FastAPI` class as normally.